Case Study: Papilloma Virus in Puppy
A 6-month old, neutered male Miniature Pinscher named Ralf presented for evaluation of itching at his legs and tail for two weeks duration. He was eating and drinking normally, current on all vaccines and heartworm test and prevention. His littermate is showing no signs of scratching and appears completely normal.
Ralf was bright and alert at the hospital and was not scratching during the physical exam. His temperature, pulse, respiration (TPR) was normal and his weight was appropriate for his age and size. His skin showed signs of hyperpigmentation along his back and abdomen. He had visible lesions of varying sizes on skin not covered with fur. He also had pustules and erythema along the base of his tail and extending along his hind-limbs. The hyperpigmented areas appeared almost freckle-like. The skin was not raised or inflamed but the lesions were numerous. No fleas or flea dirt was seen. The owner reports cleaning the dog kennel with diluted bleach.
Differential diagnosis included demodex, sarcoptes, atopy, pyoderma, ectoparasites, fungal infection, autoimmune disease.
Skin scrape (multiple sites): neg
Skin impression: neg
Fungal culture: neg
Skin punch biopsy (two sites):
First site: Pigmented epiderma plaque.
Second site: Hyperplastic, superficial, perivascular, Lymphoplasmacytic, plasmocyctic, mastocytic, neutrophilic dermatitis with surface neutrophilic exudative crusting.
Discussion points to consider
What does the pathology report mean?
What preventative measures/treatments should be instituted regardless of the negative results mentioned above?
At this point both the dog and owner are miserable due to the constant itching. What can you do safely to control this for them?
In this case, the pathology report does not show any signs of autoimmune disease. Pigmented epidermal plaques are thought to be of papilloma viral origin. They can be multifocal and in most cases remain indolent although they can regress or in rare cases progress to carcinoma. The second biopsy represents an inflammatory response within the dermis. It appears to be hypersensitivity-induced with a secondary pyoderma. Lesions could be secondary to food allergy, atopy or flea allergy. Treatment for this case was all inclusive. The pet was put on Hill's Prescription z/d diet as a food trial for eight weeks. They also started on monthly flea control for all pets in the household. Concurrently treatment with ivermectin for sarcoptes was instituted, as sarcoptes mites are rarely seen on biopsy specimens.
Intensely pruritic pets are often treated prophylactically with ivermectin. The owners understood that due to the intense nature of the itching, multiple avenues were being considered at the same time and at first it would be difficult to determine what, i.e., flea control, food trial, ivermectin treatment) was actually addressing the problem. At a two-week check-up, the dog was doing a little better, although he still had some pyoderma present. At four-week follow-up the dog was doing great. The hyper-pigmented areas were still present but there were no new lesions. At a five-month re-check the dog was still on Hill's z/d and not scratching. The owner was committed to feeding the dog Hill's z/d because he liked it, but believed the diluted bleach cleaning solution was the main problem in this case.
Papilloma virus causes skin tumors in the dog. In the young dog, skin tumors are caused by a DNA virus and are multiple in nature. They are host species specific.1 They often appear as cauliflower-type growths around the mouth, mucous membranes and occasionally the ear.2 Papillomas in the young dog often regress spontaneously. In this case, the viral presentation was a flat dark pigmented circle. Atopy in the young dog can be difficult to isolate as to specific cause. Typically, a food trail involves using substantiated hypoallergenic food for a minimum of eight weeks without any additional food substance in the diet. After the eight weeks, the original food can be re-introduced to see if pruritus develops.3
Kirpensteijin J. Treatment of Aural Neoplasia in Dogs and Cats. IVIS-Proceedings of NAVC-Volume 20, 2006.
Carter GR, Wise DJ, Flores EF. A Concise Review of Veterinary Virology. IVIS, 2005.
Tilley L, Smith F. The 5 Minute Veterinary Consult. Williams and Williams, 1997. pp. 134-135.